Luigi Galvani's experiments with frog's legs inspired Allessandro Volta, who became the first to produce energy from chemistry. His Voltaic piles -- sandwiches of brine-soaked felt between plates of silver and zinc -- are known today as batteries. Rudolf Clausius reckoned that gas molecules collide with each other as well as with the walls of their container, which explained why it takes time for the scent of a peeled orange to reach the other side of a room. The discovery of electrons as negatively charged particles within atoms helped explain the organization of the periodic table.

Galvani's frog united chemistry, physics

THE UNION of physics and chemistry began with the twitching of a frog's leg. In the 1790s Luigi Galvani lay a dead frog on a table. Also on the table was a static electricity generator. An assistant accidentally touched the nerves of the frog with a scalpel and the muscles of the frog contracted convulsively.

Galvani experimented afterward, fastening brass hooks in the legs of frogs and hanging them on an iron railing in his garden. He observed legs contracting "not only when the lightning flashed but even at times when the sky was quiet and serene."

Galvani concluded that there was a new type of animal electricity inherent in the nerves and muscles of the frog and published the results of his experiments.

Galvani died in sorrow and poverty after being fired from his professorship for refusing to swear allegiance to Napoleon, but his work inspired physicist Alessandro Volta.

Volta interpreted the results differently. He attributed the muscle twitches to an electrical current flowing between two dissimilar metals.

The frog's leg was merely a conductor.

Volta became the first individual to produce electricity from chemistry in 1796 by making a Voltaic pile, a sandwich of brine-soaked felt between plates of silver and zinc. Today we call them batteries, which differ from Volta's original only in the material used.

Ironically, Napoleon declared Volta's work a triumph and awarded him a gold medal.

In 1800, William Nicholson, an English chemist built a battery using Volta's specifications, and discovered that placing wires from the battery in water breaks down the water into hydrogen and oxygen.

Nicholson became the first man to produce a chemical reaction by electricity, a process now called electrolysis.

At the end of the 18th century chemists thought that the key to understanding chemical reactions lay in a quantitative study of what were called "affinities."

It was clear that there was a deep underlying relation between electricity and chemical affinity, but no one could have guessed that understanding would come a century later via the gas laws, Newtonian physics, conservation of energy, a new form of mathematics, and the discovery of fundamental electric charges embedded within the atom.

In 1803 John Dalton published his atomic theory, which explained the way in which chemicals combine by proportional fixed weights.

Although readily adopted as a way of understanding chemical reactions, many chemists saw atoms only as theoretical models lacking physical reality and most physicists didn't accept the model at all.

In early years of the 19th century Humphry Davy at The Royal Institution in London isolated eight now common chemical elements for the first time by separating them from solution by electrolysis.

As important as his chemical discoveries were, some have said Davy's most important discovery was his prodigal assistant, Michael Faraday.

Faraday's training was in chemistry, but he is best known for his law of electromagnetic induction, which James Clerk Maxwell used to develop the mathematics of electromagnetism and light half a century later.

Faraday, born to a poor, unemployed blacksmith, was apprenticed to a London bookbinder at age 14. He was dyslexic, wrote and spoke with great difficulty, had an unreliable memory and did not do well in the symbolic language of mathematics.

He schooled himself by reading the books in the bindery, taking notes and ingesting as much knowledge as possible.

Although disdained by the physics community for his poor mathematical ability, he was nonetheless the consummate scientist, keeping detailed notebooks of his many experiments in many aspects of electricity and chemistry.

Faraday discovered two laws of electrolysis that defined the fundamental unit of electricity.

The first law states that the weight of the element deposited or liberated is directly proportional to the amount of charge that passed through the solution.

The second law states that a given amount of charge will deposit or liberate different weights of different elements, proportional to the equivalent weights, or combining weights.

The implication is that if matter comes in packets (atoms), then electricity must also come in packets (later called electrons).

During the 19th century many new discoveries were made in chemistry, culminating with Mendeleev's periodic table in 1869. One of these was the establishment of the gas laws, which state the relationship between pressure, volume, and temperature of gases.

Meanwhile, around 1850, James Joule was perfecting the concept of conservation of energy while also "pushing" the kinetic theory of gases, which attributes the relationships of the gas laws to forces exerted on the walls of their containers by fast-moving gas molecules.

Despite Joule's efforts, the physics community remained indifferent to kinetic theory until Rudolf Clausius, a German physicist of high renown, used Newtonian physics to derive the gas laws and then to calculate the average speed of an air molecule at room temperature, which is about 1000 miles per hour.

Clausius' results caused notice, but also called into question why it takes some time for the scent to reach the opposite corner when one peels an orange in a corner of a room. At the calculated speed the scent molecules should spread throughout the room almost instantaneously.

The question prompted Clausius to reckon that the gas molecules collide with each other as well as with the walls of the container and their motion was thus hindered by these continual collisions that sends them off randomly in all directions.

Clausius introduced the concept of the "mean free path" (the average distance traveled by a molecule between collisions) and derived a formula for it.

Evidence was mounting for the existence of atoms as real objects rather than the models that chemists used as devices for calculations and physicists scorned. Were it not for the high regard for Clausius, his work might have been ignored.

In England, Clausius' paper was read by a young James Clerk Maxwell. He started working on the mathematics to calculate many measurable properties of gases such as viscosity, diffusivity, specific heat, conduction coefficient and the distribution of speeds of molecules of a gas in thermal equilibrium.

Statistical mechanics was thus born, and was later used by Einstein to explain Brownian motion, which convinced the remaining skeptics of the existence of atoms.

But it was the discovery of the electron as a negatively charged particle within the atom that brought the electrochemical connection full circle.

The properties of atomic electrons explained the organization of the periodic table, and also explained how and why atoms combine the way they do during by electrical interactions.

As esoteric as all of this may be, and despite this acutely abbreviated recollection of events, Galvani's twitching frog ultimately united chemistry and physics and with it heat, light, the gas laws, and atoms.

The strength of the resulting paradigm that defines modern physical science is a direct result of the diversity of methods by which we have arrived at it.

Richard Brill picks up where your high school science teacher left off. He is a professor of science at Honolulu Community College, where he teaches earth and physical science and investigates life and the universe. He can be reached by e-mail at rickb@hcc.hawaii.edu.